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FreeBSD-EN-22:24.zfs                                      Errata Notice
                                                          The FreeBSD Project

Topic:          ZFS snapshot directories not accessible over NFS

Category:       core
Module:         zfs
Announced:      2022-11-01
Affects:        FreeBSD 13.1
Corrected:      2022-10-27 12:00:01 UTC (stable/13, 13.1-STABLE)
                2022-11-01 13:28:11 UTC (releng/13.1, 13.1-RELEASE-p3)

For general information regarding FreeBSD Errata Notices and Security
Advisories, including descriptions of the fields above, security
branches, and the following sections, please visit
<URL:https://security.FreeBSD.org/>.

I.   Background

ZFS is one of several filesystems available on FreeBSD.  ZFS supports
many advanced features, including checksumming, transparent compression,
and snapshots.

Snapshots of a ZFS dataset can be accessed through a hidden directory,
.zfs/snapshots, located in the root of the mounted dataset.

II.  Problem Description

A kernel regression caused all dataset snapshot directories to become
inaccessible over NFS.  Any attempt to access individual snapshots would
return an error message mentioning a stale file handle.

III. Impact

Workflows which rely on ZFS snapshots being accessible over NFS are
broken.

IV.  Workaround

No workaround is available.

V.   Solution

Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date and reboot.

Perform one of the following:

1) To update your system via a binary patch:

Systems running a RELEASE version of FreeBSD on the amd64, i386, or
(on FreeBSD 13 and later) arm64 platforms can be updated via the
freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install
# shutdown -r +5min "Installing errata update"

2) To update your system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/EN-22:24/zfs.patch
# fetch https://security.FreeBSD.org/patches/EN-22:24/zfs.patch.asc
# gpg --verify zfs.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

This issue is corrected by the corresponding Git commit hash or Subversion
revision number in the following stable and release branches:

Branch/path                             Hash                     Revision
- -------------------------------------------------------------------------
stable/13/                              562c9ac58c76    stable/13-n252848
releng/13.1/                            7ab877cb3f9d  releng/13.1-n250159
- -------------------------------------------------------------------------

Run the following command to see which files were modified by a
particular commit:

# git show --stat <commit hash>

Or visit the following URL, replacing NNNNNN with the hash:

<URL:https://cgit.freebsd.org/src/commit/?id=NNNNNN>

To determine the commit count in a working tree (for comparison against
nNNNNNN in the table above), run:

# git rev-list --count --first-parent HEAD

VII. References

<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=266236>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-22:24.zfs.asc>
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